A leading law specialist says a Malaysian diplomatic accused of sex crime could - if convicted and given a custodial sentence in New Zealand - do his time back home in Malaysia.

Associate professor of law at Auckland University, Bill Hodge, agrees with that scenario but says there would have to be some delays.

"The New Zealand government won't want to be seen to be sending him back to serve his time in Malaysia just prior to the September election," Prof Hodge says.

"It makes sense, but later in the year."

Prof Hodge says the last thing John Key would want is to look like former Labour Prime Minister David Lange, who allowed Rainbow Warrior bombers Alain Mafart and Dominque Prieur - both French army officers - to serve their manslaughter sentence in Tahiti.

Malaysian authorities have said Warrant Officer Muhammed Rizalman Bin Ismail would be returned to New Zealand by a senior military officer to stand trial on charges of burglary and intent to rape - offences which are punishable by up to ten years jail.

He was spirited out of New Zealand the day after his first Wellington court appearance in May, invoking diplomatic immunity.

Prof Hodge agreed with the scenario that the Malaysian military are likely to grill the officer to establish from him if he was guilty as charged.

He agreed that if that was the case it is possible the officer may have been told or advised to admit his guilt in New Zealand and take his punishment - thus minimising any further embarrassment to both governments and distress to the 21-year old complainant."That makes sense," Prof Hodge says.

An early guilty plea is taken into consideration when sentencing an offender.But if the officer pleaded not guilty, went to trial, was found guilty and given a custodial sentence, then a similar scenario is possible but with a likely stiffer penalty.